Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By providing – treating or protecting environment – e.g. – vacuum
Patent
1995-08-07
1997-04-08
Kastler, Scott
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By providing, treating or protecting environment, e.g., vacuum
75385, C21C 710
Patent
active
056184905
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum plant, in particular for secondary metallurgy, having at least one steam ejector which is in communication with a closed container within which a metallurgical vessel which is to be subjected to a vacuum can be brought. The vacuum plant further has a second steam ejector connected in series with the first steam ejector via an intermediate condenser having a cooling-water feed line and a condensate discharge line. A final condenser and a suction pump are connected in series to the second steam ejector.
2. Description of the Prior Art
Vacuum plants which are to subject large volumes in the shortest possible time to a pressure of about 0.5 mbar are presently used in the metallurgical industry. For the drawing-off of air, steam ejectors are employed, at least two of which--and frequently three--depending on the design of the plant, are connected in series without an intermediate condenser. These steam ejectors have centrally arranged nozzles which are operated with steam.
The working agent, steam, in this connection drives air or gas in a known manner. While pure air or gases are still being drawn-in in the first stage, a mixture of steam and air or gas which must be driven by the steam working agent in the second stage, leaves the first stage. In each further stage, the proportion of steam in the driving fluid increases, with the result that the use of the driving agent must be increased in each following stage. In this way, the overall efficiency of the vacuum installation decreases. To be sure, the efficiency of the individual ejector stages is about equal and the increasing amount of steam in each stage causes a substantial impairment of the efficiency of the plant.
In order to reduce the steam content of the driven fluid, condensers are employed. As cooling water, untreated industrial water is generally employed. With this cooling water, it is not possible to remove the desired, once-established amount of moisture from the working fluid at low pressures or to condense the steam, since this cooling water has at least ambient temperature and the pressure in the condenser can in no case be brought below the vapor pressure corresponding to the temperature of the cooling water.
SUMMARY OF THE INVENTION
The object of the present invention is to create a vacuum installation of the above-discussed type in which a process-optimized production of vacuum of large containers is possible, independent of climatic influences, with a minimum of structural parts.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a vacuum plant having a closed container configured to receive a metallurgical vessel to be placed under vacuum. At least one steam ejector is in communication with the closed container and a further steam ejector is connected in series with the at least one steam ejector. An intermediate condenser is connected between the at least one steam ejector and the further steam ejector, and has a feed line and a condenser discharge line. A final condenser and a suction pump are connected in series to the further steam ejector. A heat exchanger is connected in the condensate feed line of the intermediate condenser, and the condensate feed and discharge lines of the intermediate condenser form a closed circuit. The final condenser has a condensate feed line which is in communication with the condensate discharge line of the intermediate condenser.
In the vacuum plant of the invention, a condenser is used which is cooled by a cooling system to temperatures below ambient temperature. In the case of the use of a mixing condenser, the cooling water flowing into the condenser is previously cooled. Due to the lower temperatures in the condenser, one can operate at lower pressures than in traditional installations. In this way, there is already condensed out at an earlier time drive steam which in the known systems had to be compressed with air or gas with a con
REFERENCES:
patent: 3642384 (1972-02-01), Huse
patent: 3700429 (1972-10-01), Ramachandran
patent: 4251269 (1981-02-01), Hoshi et al.
Kastler Scott
Mannesmann Aktiengesellschaft
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